This is a phase I/II study evaluating the safety, pharmacokinetics and efficacy of PMPA in HIV-1 infected patients. PMPA is a novel nucleotide analog which has been shown to be very potent in animal models. PMPA will be infused over 30 minutes. Extensive pharmacokinetic, safety and viral RNA sampling will be done during 2 weeks of study and 4 weeks of follow- up.